CMC Blade Outer Air Seal Coatings for High-Temperature Leakage Control
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Solution Overview
Problem
Existing gas turbine engines face challenges in maximizing combustion product efficiency due to leakage through blade outer air seals, particularly at high temperatures, where ceramic matrix composites are used but require improved sealing mechanisms.
Innovation Solution
A blade outer air seal formed with ceramic matrix composite materials, featuring a bond layer and a machinable seal layer with a defined thickness ratio, is applied to the mount arms, enhancing the sealing capability by using materials like rare earth silicates and mullite, and a spring bias for improved contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ceramic matrix composites are used for blade outer air seal, then high temperature resistance is improved, but sealing capability deteriorates
Solution Approach 1:
The patent applies composite materials by combining ceramic matrix composite (CMC) mount arms with a multi-layer coating system consisting of a bond coat and a seal coat. The CMC provides high temperature resistance while the deposited seal layers provide the necessary sealing capability, creating a composite structure that resolves the contradiction between heat resistance and sealing performance.
Solution Approach 2:
The patent applies local quality by depositing seal layers (bond coat and seal coat) only at specific locations on the CMC mount arms where sealing is required. The CMC material itself is used for the structural mount arms where high temperature resistance is needed, while the seal coats are applied locally at sealing surfaces to provide sealing without compromising the overall high temperature performance.
2Reliability
If seal layer thickness is increased, then sealing capability is improved, but structural integrity deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness ratio of the seal layer to the mount arm width within a specific range (0.4 to 0.8). This controlled parameter adjustment ensures sufficient sealing capability while maintaining the structural integrity of the CMC mount arm, resolving the contradiction between sealing performance and structural strength.
3Reliability
If coating is added to CMC mount arm, then sealing capability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating the seal layers (bond coat and seal coat) into the manufacturing process of the CMC mount arms. The coatings are deposited during fabrication rather than as separate post-processing steps, which integrates the sealing function into the base structure manufacturing and reduces overall manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides enhanced sealing, reducing leakage and improving the efficiency of gas turbine engines by maintaining structural integrity and thermal resistance at high temperatures.
Implementation Method 1
a bond layer deposited on the mount arm, and a seal layer is deposited on the bond layer
Data Source
Figure 1
Figure 2A~3
Figure 4A~4D
AI summary
A gas turbine engine (20) includes a compressor section (24), a combustor section (26) and a turbine section (28) for rotation on an axis (A). The turbine section (28) includes at least one row of rotating turbine blades (102) each having a radially outer tip (103). A blade outer air seal (105) is positioned radially outwardly of the radially outer tip (103). The blade outer air seal (105) has a central web (124) positioned radially outwardly of the radially outer tip (103). The blade outer air seal (105) has an upstream mount arm (120) and a downstream mount arm (122) receiving mount structure (110) from a static structure (110). The static structure (110) has sealing members (150) engaging an upstream outer surface of the upstream mount arm (120) at an upstream seal material (160) and a downstream outer surface of the downstream mount arm (122) at a downstream seal material (162). A method is also disclosed.